Sparkes J.,University of New England of Australia | Fleming P.J.S.,University of New England of Australia | Fleming P.J.S.,Vertebrate Pest Research Unit | Ballard G.,University of New England of Australia | And 4 more authors.Zoonoses and Public Health | Year: 2015

Currently, Australia is free from terrestrial rabies but an incursion from nearby Indonesia, where the virus is endemic, is a feasible threat. Here, we aimed to determine whether the response to a simulated rabies incursion would vary between three extant Australian dog populations; free-roaming domestic dogs from a remote indigenous community in northern Australia, and free-roaming domestic and wild dogs in peri-urban areas of north-east New South Wales. We further sought to predict how different management strategies impacted disease dynamics in these populations. We used simple stochastic state-transition models and dog demographic and contact rate data from the three dog populations to simulate rabies spread, and used global and local sensitivity analyses to determine effects of model parameters. To identify the most effective control options, dog removal and vaccination strategies were also simulated. Responses to simulated rabies incursions varied between the dog populations. Free-roaming domestic dogs from north-east New South Wales exhibited the lowest risk for rabies maintenance and spread. Due to low containment and high contact rates, rabies progressed rapidly through free-roaming dogs from the remote indigenous community in northern Australia. In contrast, rabies remained at relatively low levels within the north-east New South Wales wild dog population for over a year prior to an epidemic. Across all scenarios, sensitivity analyses revealed that contact rates and the probability of transmission were the most important drivers of the number of infectious individuals within a population. The number of infectious individuals was less sensitive to birth and death rates. Removal of dogs as a control strategy was not effective for any population modelled, while vaccination rates in excess of 70% of the population resulted in significant reductions in disease progression. The variability in response between these distinct dog groups to a rabies incursion, suggests that a blanket approach to management would not be effective or feasible to control rabies in Australia. Control strategies that take into account the different population and behavioural characteristics of these dog groups will maximise the likelihood of effective and efficient rabies control in Australia.

The Grey-headed Flying-fox, Pteropus poliocephalus, is listed as a threatened species in NSW, Victoria and nationally. The Grey-headed Flying-fox is a key species in maintaining forest ecosystems through the pollination of native trees and the dispersal of rainforest seeds. This threatened species is unique in that it is also recognised as a horticultural pest, predominantly in coastal orchards of south-eastern Australia. In times of native resource (pollen, nectar and rainforest fruits) shortage, flying-foxes are known to utilise commercial fruit crops. As such, the species is affected by control techniques employed by horticulturists to mitigate flying-fox damage, including shooting and netting. The NSW Department of Environment and Climate Change and the NSW Department of Primary Industries are working collaboratively to investigate flying-fox damage to commercial crops, quantify the levels of flying-fox damage (temporally and spatially), determine the factors contributing to trends in crop damage, and assess the effectiveness of mitigative measures employed by horticulturists to reduce flying-fox damage.The project is funded for two financial years through the Australian Government's Natural Heritage Trust Strategic Reserve funding and State Government contributions (cash and in-kind), and addresses several recovery actions of the draft National Recovery Plan for the Grey-headed Flying-fox. The project proposal was also strongly supported by the NSW Flying-fox Consultative Committee. The project commenced in October 2006 and focuses on commercial crops in the western Sydney Basin. To date (May 2007), preliminary evaluations have been conducted, including total yield loss, damaged fruit (including that specifically attributable to flying-foxes and birds), flyingfox crop visitation indices and crop architecture.These parameters will be compared throughout the fruit season across different stone fruit and apple crop types and between netted and unnetted crops to examine spatial and temporal trends. The process of establishing and implementing the collaborative project is discussed, within the framework of flying-fox conservation and management in NSW.

Instrinsic variation in the availability of food to animal populations reflects the influence of foraging by the animals themselves. Instrinsic variation in food availability provides a link between population density, subsequent food availability and variation in the rate of population increase (r), operating through density-dependent food shortage. In contrast, extrinsic variation in food availability is caused by environmental influences on food or animal abundance, which are independent of animal foraging. Extrinsic variation in food availability is random relative to that arising through intrinsic shortage. Intrinsic and extrinsic variation in food availability can influence animal populations simultaneously. Intrinsic variation will impart a tendency towards an equilibrium between animal and food abundance. which will be progressively obscured by density-independent variation as the influence of extrinsic factors increases. This study used a large-scale field experiment, in which the density of food-limited feral pig (Sus Scrofa L.) populations was manipulated on six sites, to assess the relative influence of intrinsic and extrinsic variation in food availability. The experiment evaluated the influence of pig population density on r and the abundance of food resources measured as pasture biomass. It was predicted that if intrinsic shortages dominated variation in food availability, pasture biomass and r would decline with increasing pig density. If extrinsic factors dominated variation in food availability, pig density would have no systematic effect on either pasture biomass or r. If intrinsic and extrinsic sources simultaneously affected variation in food availability, higher pig densities would have no systematic effect on r, but would reduce pasture biomass. The simultaneous model predicts reduced pasture biomass because, in the absence of compensatory changes in other sources of variation, the effects of intrinsic and extrinsic factors will be additive. To examine further the degree of interdependence in pig and pasture abundance, a series of stochastic models of the grazing system were estimate and the feedback loop comprising the functional and numerical responses of feral pigs to variation in pasture biomass was manipulated. In the large-scale experiment, neither pasture biomass nor r declined with increasing pig density, suggesting that food availability was dominated by extrinsic factors. However, limitations of the experiment meant that a minor decline in pasture biomass may have gone undetected. Comparison of simulation models, which included and omitted pasture offtake by pigs, indicated that because they were less efficient grazers and persisted at lower average densities relative to other large herbivores, pigs had little influence on variation in pasture biomass.